Daily intake of manganese by the adult population of Mumbai

Abstract

The daily intake of manganese (Mn) estimated through air, water and duplicate dietary analysis is found to range from 0.67 to 4.99 mg with a mean value of 2.21 mg. Ingestion through food contributed to the predominant fraction of the intake. The turnover rate of Mn through blood is approximately 2 h, based on the mean concentration of Mn in blood of 1.54 μg l⁻¹. The average concentrations of Mn in water and air were approximately 1.42 μg l⁻¹ and 37 ng m⁻³, respectively. The daily intake of Mn by the adult population of Mumbai is closer to the lower bound of the recommended limit of 2–5 mg. Electro Thermal Atomic Absorption Spectrophotometry (ET-AAS), has been used for the determination of Mn in a variety of environmental and human biological fluids. The detection limit of Mn for a volume injection of 20 μl is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities (0.5–10 ppm) and is found to be within ±8%. The reliability of estimation is further assessed through the analysis of Standard Reference Materials (SRMs) of soil, hay, milk powder and fish tissue obtained from IAEA.

Introduction

Man’s essential requisites of air, water and food contain trace amounts of a wide range of heavy metals, some of them have a significant role in several biochemical processes, whereas others are contaminants (Pirrone and Keeler, 1996, Raghunath et al., 1997, Tripathi et al., 1999). Manganese is an essential trace element for humans to maintain normal metabolism. Manganese intake through food must be, in general, sufficient to prevent deficiency (Donna and Baldwin, 1997). The best-defined deficiency symptom observed in animals relate to skeletal abnormalities where the organic matrix of bones and cartilage tend to be poorly developed (Fardy et al., 1992). Manganese is subjected to delicate homeostatic control and approximately 3–5% of ingested Mn is absorbed and it is rapidly cleared from the blood through the liver. It has been established that the whole blood Mn is a valid indicator of body Mn status and can be used for the diagnosis of diseases when the metabolism of trace element is disrupted (Greger, 1998). At a lower level, manifestations of Mn deficiency occur while high levels of Mn exposure are associated with neurologic and neuropsychiatric disorders (Donna, 1999). Chronic exposure to Mn causes neurophysiological abnormalities (Kaji et al., 1993). Thus, the information on the intake levels of Mn is important in assessing the risk to human health.

Due to its very low concentrations in a variety of environmental and biological samples such as air, water, food, serum and urine; any analysis requires the use of an accurate analytical method with sufficient sensitivity. The sensitivities offered by methods such as energy dispersive X-ray fluorescence (EDXRF), atomic emission spectrometry with inductively coupled plasma excitation (AES-ICP) are not sufficient for accurate determination of Mn at concentrations usually encountered in biological samples (Willium, 1998, GBC, 1994). The ET-AAS technique offers the required sensitivity levels and can determine Mn in biological sample matrices in parts per billion levels. The purpose of this study is to standardize a reliable method for the determination of Mn in a variety of environmental materials such as water, air particulate, duplicate diet, blood and urine for estimating its daily intake and turn over rate in the adult population of Mumbai.